Senior officials from the National Disability Insurance Scheme are not ruling out tightening access to people with autism trying to access the $22 billion program.
Chief executive of the National Disability Insurance Agency, Robert De Luca, has confirmed work is under way to consider conditions around automatic entry to the scheme.
Labor senator Murray Watt pressed Mr De Luca during a budget estimates hearing for a guarantee that people with level two autism will not be removed from a list of those who automatically qualify for taxpayer-funded support.
"No, I cannot guarantee that, senator," Mr De Luca told the hearing in Canberra on Friday.
Social Services secretary Kathryn Campbell said the department could never rule out changes to the NDIS.
"We have said constantly that we have to refine the system as it rolls out to make sure those people who are eligible for the scheme have access to the scheme," she told senators.
Disability advocates have raised serious concerns about potential moves to restrict access of autistic people to the NDIS in recent weeks.
Their fears stem from an updated operational guideline, accidentally uploaded to the NDIS website in mid-May.
A staffer at the disability agency altered a list of conditions for autism spectrum disorder, which would require a higher level of evidence to qualify for NDIS support.
The changes would remove people with level two autism from "List A" for automatic qualification, meaning they would be required to be independently assessed before qualifying for support.
Mr De Luca said the "incorrect" changes were made without proper oversight, and the document was removed and replaced as soon as the agency was aware.
"I regret we got ourselves into a position that we shouldn't have got into, and caused anxiety in a sector in the community that we didn't need to," he told senators.
"I'm confident that we've developed a much more rigid and structured change-management process to any changes going forward."
There are 160,000 participants in the disability scheme and 29 per cent have autism.
Social Services Minister Dan Tehan has since tried to ease the concerns of participants.
"I can assure you that no change will be made to the NDIA's operational guidelines, including List A, unless those changes are informed by research, evidence and extensive consultation with stakeholders and the community," Mr Tehan wrote in a letter to stakeholders.
Australian Associated Press